SG Junior upgrades

[Dmoney]

I don't fully understand the dummy coil. Surely it has to be mounted in some relative way to the pickups? The the blueshawk it has a route parallel to the P90's sort of like the middle pickup on a strat. I don't see how you'd get the hum cancellation by mounting a coil in the control cavity. Maybe I'm missing something. I read a page saying that the dummy coil is demagnetised too, but I assume that just means the core is much lower flux density rather than absolutely zero.

[Kiichi]

I don't fully understand the dummy coil. Surely it has to be mounted in some relative way to the pickups? The the blueshawk it has a route parallel to the P90's sort of like the middle pickup on a strat. I don't see how you'd get the hum cancellation by mounting a coil in the control cavity. Maybe I'm missing something. I read a page saying that the dummy coil is demagnetised too, but I assume that just means the core is much lower flux density rather than absolutely zero.

Way I think about it it has to be in the cavity to do its job without changing the sound too much. It is about having too coils with the same hum so they can cancell it out, right? But I only want the hum from that extra coil, no other stuff chaning the sound when you add those together. Thus putting it under the strings seems defeating part of the purpose. I would guess that parallel still makes sense though in that magnetic fields or so might effect them in the same way.

[Dmoney]

Well I see your point. I guess the dummy coil doesn't need to be magnetic at all, it just needs to act as an aerial which has noise induced into it from external sources in an out of phase direction to the noise in the real P90's. If the coil is totally demagnetised then it wouldn't effect the sound as it would have no magnetic field at all. That said, it's interesting that gibson mount the coil under the strings... maybe someone got it wrong? If that is the case... how does it work if you mount the coil in a shielded cavity because then it would be theoretically isolated from any noise wouldn't it?

[Kiichi]

Yeah, now you really got me confused. I was mostly guessing before and trying to make sense of what people do...now you got me thinking...and it hurts xD

[Dmoney]

See! haha.

Now... how to make it work if your P90 set has has a RWRP pickup, because the dummy coil would end up creating noise which is IN phase with one pickup... right? Maybe I'm wrong again.

[Philly Q]

Philking tried some hum-cancelling P90s in his WezV SG. I tried said guitar also. They sounded sadly sterile. I forget which brand they were, but it was a boutique brand of some sort.

Don't P100s sound quite sterile too?

P100s sound absolutely rubbish.

[Guitarteach]

I just temporarily wired in a spare Ibanez SC i had in parallel with my P90 and stuffed it in the control cavity (just needs to be on same horizontal to the P90 to 'buck' the same interference.)

Amazing trick - hum 90% gone and no real impact on tone as it does not add any signal.

I am frankly amazed... So I am going to solder it in permanently via a push/push so i can switch it out for the non Hi-Gain stuff.

Def. recommended to try. Fyi. My control cavity is not shielded so i suspect a shielded cavity could prevent it working same.

I could imagine a market for nice potted magnet free dummy coils to supplement classic P90s for high gain use.

[gwEm]

guitarteach:

thats pretty interesting - so to be 100% sure, you used basically a strat sized coil to cancel hum from a P90?

[Guitarteach]

Yep. I have not checked resistance and inductance though for a mathematically correct fix - but testing it wired in parallel it seems to have worked. It was an Ibanez Inf SC

Its basically an inverse aerial to kill noise that does not generate any additional musical signal from the strings.

I am sure there are better options but I was not considering changing my P90s as they would still be noisy - so i was intrigued to test this. Now i can see options to have high gain switch to kill the hum as I would not want to compromise the great low gain sounds.

[gwEm]

These dummy coils are very cool, but they seem quite invasive. Maybe I would try an Electro Harmonix 'Hum Debugger' pedal first.

[Alex]

The Boss NS-2, which is often criticised for its performance in effects loops, did a decent job for me for dealing with Single coild noise/hum/feedback when I had a Strat.

[Dave Sloven]

The Boss NS-2, which is often criticised for its performance in effects loops, did a decent job for me for dealing with Single coild noise/hum/feedback when I had a Strat.

Did you have the pedal in front of your amp?

[Dave Sloven]

Well, I can say two things after a decent play with it today. (1) It doesn't sound any worse; (2) though it's hard to tell as the shielding didn't put the slightest dent in the screeching feedback and my ears are ringing again.

The issue isn't hum per se, it's the fact that every noise the guitar makes - hum included - feeds back like crazy under high gain.  If I can find a way to stop hum theoretically that might eliminate the feedback that I can't control by muting the strings.

I'm thinking of trying the Hum Debugger even though people say that it affects tone.  TBH I can't hear such small differences in tone over screeching feedback!

I'm more worried about the impact on my wallet ...

What does a microphonic noise sound like?  I'm not sure if I've ever heard it or not. I do know that the guitar is very resonant and the pickup picks up every tap, knock, or turn of a screw

[gwEm]

If its screeching under high gain its still 95% sure the pickup is microphonic.

Does it stop when you turn the guitar volume down?

[Dave Sloven]

I've just sent an email to Ben.  This guitar is threatening to do my ears in.  They are still ringing!

Possible its microphonic but I'm pretty sure I got some wax out of the pole piece screws when I turned them before, so I think it was potted.  Question is I guess whether there's some kind of air pocket in the wax.

Also it uses the 'batwing mount' (you might be able to see that in one of the photos) so it mounts to the pickguard like a regular humbucker does in a batwing SG but I did put foam under it this time.

My SG Standard (Cold Sweat set) is quiet as a mouse in this respect and it has NO shielding.  The Explorer (Nailbomb set) has shielded cavities - but no wired ground for the shield, so the shield is technically not quite as good as the one in the Junior - and it feedsback very little, like when you stand a couple of feet from the amp.  The Junior squeals when you are in the same room.  Some who like to exaggerate would say 'in the same postcode' ... it does it at least as far as my 20ft cable can reach around the various corners etc, I'd say at least 15'

EDIT:

I just realized that there was no photo of the pickup mounting in this thread so here's an old photo from when I first installed the BKP, which shows the new pickup mounted to the pickguard.